The present invention relates to a stable microfoamed fruit or vegetable purée and its preparation method.
Fruit purées can have a sticky pasty texture in the mouth, with slight astringency and marked acidity. To improve the sensory qualities of the fruit purée, and to reduce the volume of sugars, microfoaming of the purée has been the chosen technology.
Foamed food systems are complex, as they are made up of varied phases dispersed in a continuous aqueous medium, such as air bubbles or sugar crystals. To ensure robustness of formulations from an industrial viewpoint, while at the same time maintaining good organolepsy of these foams, particular attention is given to formulation in order to facilitate aptitude for foaming of the foam and guarantee its stability over time.
Fruit foams having a high foaming rate (50 to 100%) are already known in the prior art. However, microfoaming does not give the same result as classic foaming. In fact, microfoaming consists of injecting a very low quantity of air (<50% in volume, preferably <30% in volume, even better 20% in volume) for the purpose of producing bubbles of very low granulometry, nearly invisible to the naked eye, such as D3.2≦less than 200 μm. The aim of this microfoaming is not to modify the macroscopic texture of the fruit or vegetable purée, as classic foaming might so, consisting of injecting 50 to 100% in air volume. On the contrary, the interest in this technology is modifying the sensory properties of the fruit or vegetable purée without modifying its visual appearance. The benefit is contributing a sort of “signature” of the fruit or vegetable purée, allowing it to stand out.
Of the ingredients utilised in making foams, the role of emulsifiers is a determinant in the process of forming the foam, while that of stabilising agents will essentially intervene in the stabilisation of the latter over its shelf life.
Gelatine occupies a place of choice among emulsifiers and the stabilising agents, in light of its multifunctional properties: in aerated systems, it plays two basic roles by acting as foaming agent, then allowing stabilisation of the aerated texture. However, its use is regularly put in question, for questions of food safety (BSE problem) or religious reasons. So replacing it is not simple.
In fact, the choice of emulsifier is important since it conditions the foaming aptitude of the fruit or vegetable purée.
Patent application WO 2004/04481 describes using seric proteins as emulsifier and in particular Lacprodan®. However, the seric proteins of Lacprodan® are not defatted. They contain around 4% by weight of fatty matter. In addition, seric proteins of Lacprodan® have been denatured since they have been pasteurised. According to the graphs of DANEBERG in the event of pasteurisation, the denaturation level of seric proteins is in general between 60 and 90%. Also, it is known that the fatty matter stabilises the resulting foams. Further, the overrun used in the foam described in this document is between 50 and 130%. For nutritional reasons there is therefore a need for fruit or vegetable foam stabilised without any fatty matter.
The U.S. Pat. No. 2,131,650 describes a fruit or vegetable foam containing the solid part of the milk serum obtained by precipitation of casein from milk. This solid part therefore contains casein as well as some lactoseric proteins, these proteins having been denatured during precipitation.
Patent application EP 1 166 655 describes a fruit foam obtained from denatured proteins. With a view to thermal treatment applied to paragraph [0021] of the document, a denaturation level between 93 and 100% is obtained. In the case of example 1, the proteins are totally denatured (denaturation level of 100%). Thus, none of the documents of the prior art describes or suggests using defatted and native seric proteins to produce a stable foam by a microfoaming method.
Yet, the inventors surprisingly found that “defatted” seric proteins, devoid of fatty matter, and native (that is non-denatured as are the by-products of the cheese industry) such as obtained by a method of microfiltration or ion chromatography exchange are excellent candidates for microfoaming of fruit or vegetable purées. These proteins remain native despite foaming, that is, they are not denatured by such mechanical treatment. In fact, according to the book by Philippe Cayot and Denis Lorient, “Structures and technofunctions of milk proteins” (Arilait recherches, Edition Lavoisier 1998, 2nd part, pages 105-203), it is only thermal treatments and the pH modifications which can denature seric milk proteins. This is otherwise confirmed by patent application EP 1 284 106, paragraph [0017] which explains that denaturation of proteins in foam occurs only after foaming.
Further, the inventors of the present application found surprisingly that in the event where seric proteins are used as foaming agent, it is not always necessary to also use a texturing agent to maintain the stability of the stable microfoamed product and prevent an increase in the size of the bubbles. In fact, the quantity of pectins present in the majority of fruit or vegetable purées is sufficient to keep the microfoamed texture throughout conservation of the product.